Fatty acids are carboxylic acids with long-chain hydrocarbon side groups and play a fundamental role in many biological processes. Fatty acids are often unhydroxylated; however, such unhydroxylated fatty acids may be converted to hydroxyl fatty acids by the introduction of at least one hydroxyl group, a process catalyzed by a hydroxylase enzyme.
Hydroxyl fatty acids and hydroxyl oils are particularly important for a variety of industrial applications. Indeed, hydroxyl fatty acids, such as ricinoleic acid (12-hydroxyoctadec-9-enoic acid), are important industrial feedstock in the manufacture of biolubricants, functional fluids, ink, paints, coatings, nylons, resins, foams and other biopolymers.
The biosynthesis of fatty acids is a major activity of plants and microorganisms. Biotechnology has long been considered an efficient way to manipulate the process of producing fatty acids in plants and microorganisms. It is cost-effective and renewable with little side effects. Thus, tremendous industrial effort directed to the production of various compounds including specialty fatty acids and pharmaceutical polypeptides through the manipulation of plant, animal, and microorganismal cells has ensued.
At present, however, castor bean (Ricinus communis) is the only commercial source for hydroxyl fatty acids. Due to poor agronomic performance and the presence of highly potent toxins (ricin) and allergens in the seed, castor bean is not an ideal source for the fatty acids. Thus, a growing demand exists for alternatives to replace castor bean as a source of the hydroxyl fatty acids (Jaworski and Cahoon, 2003). Genes involved in the biosynthesis of hydroxyl fatty acids such as ricinoleic and lesqueroleic acids have been isolated from plant castor bean (Ricinus communis) and Lesquerella fendleri (van de Loo et al., 1995) (Broun et al., 1998). Both genes encode oleate 12-hydroxylase, which introduces a hydroxyl group at position 12 of oleic acid. However, the introduction of the castor bean oleate hydroxylase into tobacco, Arabidopsis thaliana resulted in low to intermediate levels of ricinoleic acid accumulation in seeds (van de Loo et al., 1995) (Broun and Somerville, 1997) (Smith et al., 2003).
Although biotechnology offers an attractive route for the production of specialty fatty acids, current techniques fail to provide an efficient means for the large scale production of hydroxyl fatty acids. Accordingly, there exists a need for an improved and efficient method of producing hydroxyl fatty acids, such as ricinoleic acid.